Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712-0292, USA.
Applied Research Laboratories, The University of Texas at Austin, Austin, Texas 78713-8029, USA.
J Acoust Soc Am. 2023 Jan;153(1):678. doi: 10.1121/10.0017000.
Seagrasses play an important role in coastal ecosystems and serve as important marine carbon stores. Acoustic monitoring techniques exploit the sensitivity of underwater sound to bubbles, which are produced as a byproduct of photosynthesis and present within the seagrass tissue. To make accurate assessments of seagrass biomass and productivity, a model is needed to describe acoustic propagation through the seagrass meadow that includes the effects of gas contained within the seagrass leaves. For this purpose, a new seagrass leaf model is described for Thalassia testudinum that consists of a comparatively rigid epidermis that composes the outer shell of the leaf and comparatively compliant aerenchyma that surrounds the gas channels on the interior of the leaf. With the bulk modulus and density of the seagrass tissue determined by previous work, this study focused on characterizing the shear moduli of the epidermis and aerenchyma. These properties were determined through a combination of dynamic mechanical analysis and acoustic resonator measurements coupled with microscopic imagery and finite element modeling. The shear moduli varied as a function of length along the leaves with values of 100 and 1.8 MPa at the basal end and 900 and 3.7 MPa at the apical end for the epidermis and aerenchyma, respectively.
海草在沿海生态系统中起着重要作用，是重要的海洋碳储存库。声学监测技术利用水下声音对气泡的敏感性，气泡是光合作用的副产品，存在于海草组织中。为了准确评估海草生物量和生产力，需要建立一个模型来描述声传播穿过海草草甸，该模型包括海草叶片内气体的影响。为此，本文描述了一种新的塔希提海草叶模型，它由相对刚性的表皮组成，构成叶片的外壳，以及相对顺应的通气组织，包围叶片内部的气道。根据先前的工作确定了海草组织的体积模量和密度，本研究重点研究了表皮和通气组织的剪切模量的特征。这些特性是通过动态力学分析和声学共振器测量以及微观成像和有限元建模的结合来确定的。表皮和通气组织的剪切模量随叶片长度而变化，在叶片基部的表皮和通气组织的剪切模量值分别为 100 和 1.8 MPa，在叶片顶部的表皮和通气组织的剪切模量值分别为 900 和 3.7 MPa。
